Saturn’s Most Habitable Moon Offers Ice, Water, Killer Views

Enceladus has to be one of the most intriguing objects in the solar system. It’s definitely our favorite of Saturn’s 62 moons here at Wired Science, and it’s among the most likely places to find the necessary ingredients for extraterrestrial life in the solar system.

Enceladus actively spews jets of material from its south pole, forming one of Saturn’s majestic rings. New evidence from the jets suggesting that there is a liquid ocean beneath the moon’s icy crust was published just this week in the journal Icarus.

Data from NASA’s Cassini spacecraft, which dove through the jets in 2008, showed the plumes contain negatively charged ions, which have only been found on Earth, another Saturnian moon — Titan — and comets. On Earth, negatively charged ions are found where water is moving, such as in a waterfall or a crashing wave. The discovery of the ions in Enceladus’ jets is the best evidence yet of liquid water.

On top of being a possible haven for life, Enceladus is beautiful. Its icy crust is riven with cracks and folds that somehow look both familiar and alien at the same time. Older surfaces have impact craters. The four huge, linear depressions at its south pole known as the tiger stripes are probably less than 1,000 years old and warmer than the rest of the crust, evidence that Enceladus is actively forming ice.

Though it is just over 300 miles in diameter, a tenth the size of Titan, tiny Enceladus has won us over. With Cassini’s new life extension into 2017, and 11 more planned flybys of Enceladus, we can expect more awesome images and enlightening data.

Here we have collected some of the best images of Enceladus that Cassini has collected since it began exploring Saturn in 2004.

This raw image of the icy crust of Enceladus shows the ridges and valleys that cover the moon’s surface. The grooves are typically a few hundred meters wide, but some rifts can be 125 miles long, up to 6 miles wide and more than half a mile deep.

Because grooved areas such as in the photo above often have no impact craters, they must be younger than 100 million years and suggest that active tectonics has formed the moon’s crust, similar to the tectonic plate motion that shapes Earth’s crust.

Because Enceladus is actively creating fresh, clean ice, it is perhaps the most reflective body in the solar system. Reflecting so much sunlight keeps the moon below minus 325 degrees Fahrenheit, a bit colder than Saturn’s other moons.

Enceladus is seen here as a crescent resembling our own moon in an edge-on view of Saturn’s rings. Our moon is 2,159 miles across, more than seven times the size of Enceladus, which has a diameter of just 300 miles.

Craters left by asteroid impacts can be seen in the lower part of this image. Enceladus has many craters on its northern side, but it’s southern pole is relatively impact-free. This means most of the ice crust in the south is less than 100 million years old, and possibly as young as 500,000 years. If it had been around any longer, it would have been peppered with asteroids, like most of the planets and moons in the solar system.

Enceladus is one of only four bodies in the solar system where active eruptions have been seen. Earth and Jupiter’s moon Io have volcanic eruptions, while Enceladus and Neptune’s moon Triton have cryovolcanism, where water and other volatiles are erupted instead of lava and ash.

Enceladus’ southern tiger stripes are actively spewing jets of ice into space. The region is also anomalously warm relative to the rest of the planet, and releasing three times more heat than a similar sized area on Earth. Until recently, scientists didn’t know why.

A study in Nature Geoscience in January explains that the heat is caused by blobs of warmer ice moving toward the surface and pushing colder ice down. Scientists think these eras of churning ice last around 10 million years, while the intervening quiet times last 100 million to 2 billion years, so Cassini is lucky to have visited during one of the active times that make up between 1 and 10 percent of the moon’s history.

“Cassini appears to have caught Enceladus in the middle of a burp,” UC Santa Cruz planetary scientist Francis Nimmo, co-author of the new study, said in a press release. “These tumultuous periods are rare, and Cassini happens to have been watching the moon during one of these special epochs.”

Cassini flew within 1,000 miles of Enceladus in November and captured this image of the moon’s fractured surface in the region of the tiger stripe known as Baghdad Sulcus. The ridges and grooves in this photo of the surface of Enceladus look almost like mountains and valleys on Earth seen from an airplane.

This was Cassini’s last look at the moon’s southern pole before it slips into winter and several years of darkness.

This backlit beauty shot of Enceladus highlights the plumes that have intrigued astronomers. Known to contain water vapor, ammonia and organic molecules, they may also harbor clues about the moon’s habitability and the possibility of a subcrustal liquid ocean. In 2008, Cassini dove through the plumes again to gather more images and data, including information about the heat emanating from the region.

This spectacular image of Enceladus nestled next to Saturn below the planet’s rings was taken by Cassini on Christmas Day, 2009. It was captured by the spacecraft’s wide-angle camera from 384,000 miles away.